Vertebral Implant Including Preformed Osteoconductive Insert and Methods of Forming

ABSTRACT

A vertebral implant for insertion into a patient includes an insert formed from an osteoconductive material and further including a biocompatible polymer body that is formed into the insert. The insert may extend over part of or substantially the entire bone contact surface of the implant. The insert includes a bone contact surface and a substrate interface. The implant may include fibers that extend across the substrate interface from the insert to the body. The insert may be thin relative to the overall thickness of the implant. The insert may be preformed. The insert may be formed using a molding process. The body may be molded onto the insert.

RELATED APPLICATION

The present application is a divisional application of co-pendingapplication Ser. No. 11/485,259, filed on Jul. 12, 2006, andincorporated by reference herein in its entirety.

BACKGROUND

Spinal implants are often used in the surgical treatment of spinaldisorders such as degenerative disc disease, disc herniations, curvatureabnormalities, and trauma. Many different types of treatments are used.In some cases, spinal fusion is indicated to inhibit relative motionbetween vertebral bodies. In other cases, dynamic implants are used topreserve motion between vertebral bodies. In yet other cases, relativelystatic implants that exhibit some degree of flexibility may be insertedbetween vertebral bodies.

Implants such as these may be positioned between vertebral bodies, withsuperior and inferior surfaces placed in contact with the vertebralbodies. Often, the bone-contact surfaces of these implants areconfigured with a surface texture, surface features, and natural orsynthetic bone growth stimulators to promote osseointegration of theimplant. Recent innovations in implant materials have produced a newgeneration of implants constructed from polymers such as UHMWPE or PEEK.These polymer materials may offer a variety of advantages, includingimproved strength, reduced weight, and desirable mechanicalcharacteristics. Unfortunately, the polymers are not naturallyosteoconductive. Thus, implant constructed from these polymers may notsufficiently fuse with the vertebral bodies. Ineffective fusion at thebone-contact surface may lead to subsidence of the vertebral implantsover time, and often leads to spinal instability, angular deformities,and planar translations.

SUMMARY

Illustrative embodiments disclosed herein are directed to a vertebralimplant device for insertion into a patient. One embodiment of avertebral implant device may include an insert with a first bone contactsurface and an opposing second surface. The insert may be constructedfrom an osteoconductive material with fibers with some of the fibersincluding a first section positioned in the insert and a second sectionthat extends outward from the second surface. The insert may alsoinclude an anchor that extends outward from the second surface a greaterdistance than the second sections of the fibers. A non-osteoconductivebody may be attached to the second surface of the insert and may beformed from a different material than the insert. The second sections ofthe fibers and the anchor may be positioned in the body. The insert andthe anchor may have a unitary construction formed from theosteoconductive material.

An embodiment of the vertebral implant device may include a bodyconstructed from a first material with a first side and an opposingsecond side. An insert may be attached to the first side of the body andmay be constructed from a second material having a plurality of fibers.An anchor may extend outward from the insert into the body and mayinclude a stem adjacent to the insert and a head spaced away from theinsert and positioned at an end of the stem. The stem may include asmaller width than the head. The anchor and a portion of the fibers maybe positioned to extend outward from the insert and into the body toimprove adhesion between the body and the insert.

An embodiment of the vertebral implant device may also include anintermediate portion constructed of a first material and including afirst side and a second side. A first insert may be attached to thefirst side of the intermediate portion and may include a first contactsurface configured to contact against the first vertebral body when thevertebral implant device is inserted in the patient. A second insert maybe attached to the second side of the intermediate portion and mayinclude a second contact surface configured to contact against thesecond vertebral body when the vertebral implant device is inserted inthe patient. Each of the inserts may be constructed from a secondmaterial with a plurality of fibers. A portion of the plurality offibers of each of the first and second inserts may extend into theintermediate portion. A plurality of anchors may extend outward from thefirst and second inserts and into the intermediate portion. Each of theplurality of anchors may include a stem adjacent to the insert and ahead spaced away from the insert and positioned at an end of the stem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vertebral implant according to one ormore embodiments;

FIG. 2 is a top view of a vertebral implant according to one or moreembodiments shown relative to a vertebral body;

FIG. 3 is a section view of a vertebral implant according to one or moreembodiments;

FIG. 4 is a detail view of the vertebral implant of FIG. 3;

FIGS. 5A-D illustrate exemplary process steps by which osteoconductiveinserts may be formed onto an implant according to one embodiment;

FIG. 6 is a section view of a vertebral implant according to one or moreembodiments;

FIG. 7 is a section view of a vertebral implant according to one or moreembodiments;

FIG. 8 is a section view of a vertebral implant according to one or moreembodiments;

FIG. 9 is a section view of a vertebral implant according to one or moreembodiments;

FIG. 10 is a section view of a vertebral arthroplasty implant accordingto one or more embodiments;

FIG. 11 is a side view of a corpectomy implant according to one or moreembodiments; and

FIG. 12 is a side section view of an acetabular implant according to oneor more embodiments.

DETAILED DESCRIPTION

The various embodiments disclosed herein relate to a vertebral implantin which bone-contact surfaces are constructed with an osteoconductiveinsert. The number 10 in FIG. 1 generally identifies one example of animplant including an osteoconductive insert. The representativevertebral implant 10 is a disc replacement implant that is insertedbetween vertebral bodies of a patient as part of a disc replacementsurgery. The vertebral implant 10 may be constructed, at leastpartially, from biocompatible polymers, such as polyethylene, UHMWPE,and implantable grade polyetheretherketone (PEEK) or other similarmaterials (e.g., PAEK, PEKK, PEK, PEEKK and PEKEKK). The exemplaryvertebral implant 10 includes a perimeter wall 12 that extends between asuperior surface 14 and an inferior surface 16. The superior surface 14and inferior surface 16 are bone-contact surfaces in that they arepositioned adjacent to and facing a vertebral endplate once thevertebral implant 10 is inserted into a patient.

The vertebral implant 10 shown in FIG. 1 includes a kidney shape, thoughother shapes may be used. In further embodiments, the vertebral implant10 may take on other types of configurations, such as, for example, acircular shape, semi-oval shape, bean-shape, D-shape, elliptical-shape,egg-shape, or any other shape that would occur to one of skill in theart. The vertebral implant 10 may take on substantially solidconfigurations, such as, for example, block-like or plate-likeconfigurations that do not define an open inner region. In otherembodiments, the vertebral implant 10 could also be described as beingannular, U-shaped, C-shaped, V-shaped, horseshoe-shaped, semi-circularshaped, semi-oval shaped, or other similar terms defining an implantincluding at least a partially open or hollow construction.

The exemplary vertebral implant 10 includes one or more apertures 18disposed about the perimeter wall 12 that provide a location at which tograsp the vertebral implant 10 during surgical installation. In someinstances, the vertebral implant 10 is constructed of a material that issolid, but somewhat flexible or compressible. Thus, the apertures 18 maycontribute to the overall flexibility and/or compressibility of thevertebral implant 10.

FIG. 2 depicts a top view of the exemplary vertebral implant 10 orientedrelative to a vertebral body V, which is depicted in dashed lines. Thevertebral implant 10 is positioned substantially within the cortical rimR of the vertebral body V. Further, the vertebral implant 10 ispositioned in contact with one of the end plates P of the vertebral bodyV. Accordingly, the vertebral implant 10 includes a superior surface 14and an inferior surface 16 that contact the bony end plates P ofvertebral bodies V. Improved results may be obtained if the superiorsurface 14 and inferior surface 16 of the implant 10 fuse with the endplates P.

Where the implant 10 is constructed of a generally non-osteoconductivematerial, an osteoconductive insert may be formed into the implant topromote bone growth at the superior 14 and inferior 16 surfaces of theimplant 10. To that end, FIG. 3 shows a section view of the vertebralimplant 10 taken from the direction indicated by the section lines inFIG. 2. The section view in FIG. 3 shows that the implant 10 isconstructed of an intermediate portion 24 and two inserts 20, 22.Generally, the intermediate portion 24 may be constructed of anon-osteoconductive polymer while inserts are constructed fromosteoconductive materials. In one embodiment, the inserts 20, 22 areformed from a material or with a construction that provides a greaterdegree of osteoconduction than the intermediate portion 24. The inserts20, 22 are disposed at the superior 14 and inferior 16 surfaces of theimplant 10 and provide an interface surface into which bone growth ispermissible.

The inserts 20, 22 may be constructed from an osteoconductive orosteoinductive matrix that includes materials such as collagen, carbonfibers, including continuous or chopped carbon fibers. The inserts mayinclude carbon nano-fibers, or metallic filaments including titanium,tantalum, or stainless steel. The inserts 20, 22 may be constructed froma composite matrix of non-osteoconductive polymers filled withosteoconductive materials. The inserts 20, 22 may be constructed from abraided or woven fabric of biocompatible material. In general, theinserts 20, 22 may be thin relative to the overall height of the implant10. For example, the inserts 20, 22 may have a thickness between about 1and 10 mm In one embodiment, the inserts 20, 22 have a thickness betweenabout 3 mm and about 5 mm. The relatively thin nature of the insertsadvantageously permits osseointegration while preserving the overallstructural characteristics of the implant 10.

As indicated, the inserts 20, 22 may include osteoconductive fibers.These fibers 26 are depicted graphically in FIG. 4, which shows adetailed portion of the section view provided in FIG. 3. In oneembodiment, the fibers 26 are oriented randomly. In one embodiment, thefibers 26 are oriented at least partially transverse to an interfacesurface 28 between the insert 20 (or 22) and the intermediate portion24. In one embodiment, the fibers 26 extend through the interfacesurface 28 so that they are anchored in each of the insert 20 and theintermediate portion 24. The fibers 26 may include carbon fibers, metalfilaments, or fibers from a woven or braided biocompatible material.

For the various embodiments disclosed herein, FIGS. 5A-5D depictexemplary process steps that may be performed to join theosteoconductive inserts 20, 22 to the intermediate portion. The processsteps generally illustrate a molding process whereby the intermediateportion 24 is molded onto pre-formed inserts 20, 22. The inserts 20, 22may be formed through a separate molding process, including compressionmolding, injection molding, or a machining operation where the insertsare cut from stock material.

The exemplary process contemplates a mold 100 that is used to injectionmold the intermediate portion 24 onto the inserts 20, 22. Othertechniques may be used and the present illustration is provided merelyas one possible approach. In a first step shown in FIGS. 5A and 5B, thepreformed inserts 20, 22 are positioned within a mold cavity 106, 108 ofrespective mold halves 102, 104. Once the inserts 20, 22 are positionedas desired, the mold is closed as illustrated in FIG. 5B. In theembodiment depicted, the mold halves 102, 104 are substantiallyequilateral. That is, the mold halves 102, 104 form a parting line nearthe midline of the implant 10. Those skilled in the art will recognizethat more complex mold configurations including multiple components maybe required depending on implant complexity and geometry. Theillustrated mold halves 102, 104 include injection ports 110 throughwhich resin material is forced to fill the mold 100.

Once the mold 100 is closed, resin material 112 from which theintermediate portion is formed is injected through the injection ports110 and into the mold cavities 106, 108. FIG. 5C illustrates the resinmaterial 112 in fluid form partially filling the mold cavities 106, 108.After a sufficient amount of additional resin material 112 is added tocompletely fill the mold cavities 106, 108, the resin material 112 isallowed to set and harden. Once the resin material 112 has cured, themold 100 is separated and the implant 10 may be removed as shown in FIG.5D).

In the embodiment illustrated in FIGS. 3-5, the inserts 20, 22 abut theintermediate portion 24. Adhesion between the components 20, 22, 24 maybe improved via fiber orientation as shown above. Adhesion may beimproved where the inserts 20, 22 are at least partially porous so thatresin material may expand into the inserts 20, 22 during the process offorming the intermediate portion 24 onto the inserts 20, 22.Alternately, the inserts 20, 22, may include anchor features as depictedin the embodiments shown in FIGS. 6 and 7.

FIG. 6 shows an implant 10A including inserts 20A, 22A, and anintermediate portion 24A. In the illustrated embodiment, the inserts20A, 22A include a plurality of anchors 30 comprising a stem portion 32and an enlarged head portion 34. In embodiments where the injectableresin 112 comprises a curable liquid that forms the intermediate portion24A, the cured material may harden in the undercuts adjacent the stemportion 32, between the head portion 34 and the inserts 20A, 22A. Theanchors 30 may provide a more secure bond between the intermediateportion 24A and the inserts 20A, 22A.

Similarly FIG. 7 shows an implant 10B including inserts 20B, 22B, and anintermediate portion 24B. In the illustrated embodiment, the inserts20B, 22B include a plurality of anchors 36 comprising a recess 38. Asabove, the injectable resin 112 may harden in the recesses 38. Theanchors 36 may provide a more secure bond between the intermediateportion 24B and the inserts 20B, 22B.

In embodiments described above, the inserts 20, 22 have formedsubstantially the entire superior 14 and inferior surfaces 16 of theimplant 10. However, this is not expressly required. The inserts 20, 22may extend over some area that is less than the entire bone-contactsurface. For instance, FIG. 8 shows an embodiment of an implant 10C inwhich the osteoconductive inserts 20C, 22C are disposed at the superior14 and inferior 16 surfaces of the implant 10C. However, the inserts20C, 22C form less than the entire superior 14 and inferior 16 surfaces,respectively. The intermediate portion 24C forms the remaining portionof the superior 14 and inferior 16 surfaces.

In addition, there is no express limitation on the number of inserts 20,22 that are included at the bone contact surfaces of the implant 10.Thus, for example, FIG. 9 shows an implant 10D in which the superiorsurface 14 includes a plurality of osteoconductive inserts 20D, 120D. Inthe present embodiment, two inserts 20D, 120D are provided at thesuperior surface 14, though a larger number of inserts 20D, 120D may beprovided. Likewise, the inferior surface 16 includes two osteoconductiveinserts 22D, 122D, though a larger number may be included in the implant10D.

Embodiments described above have pertained to vertebral implants 10 inwhich superior and inferior bone contact surfaces are located on thesame body. However, this is not expressly required. The curvature of therespective bone contact surfaces may be disposed in separate implants orseparate implant members such as the vertebral implant 110 shown in FIG.10. The vertebral implant 110 represents a spinal arthroplasty deviceand comprises three main components: a first end plate 112, a second endplate 114, and a nucleus 116. In the orientation shown, the first endplate 112 is a superior end plate while the second end plate 114 is aninferior end plate. Each end plate 112, 114 may include a respectivebone interface surface 118, 120 that is placed in contact with acorresponding a vertebral member (not shown). The nucleus 116 ispositioned between the end plates 112, 114. The interface between thenucleus 116 and each end plate 112, 114 is a sliding interface thatallows for sliding motion of the nucleus 116 relative to the end plates112, 114. The arrows labeled A and B in FIG. 10 illustrates this slidingmotion. In the illustrated embodiment, each end plate 112, 114 isconstructed with an osteoconductive insert 130, 132 that is formed ontoa resin substrate 134, 136, respectively.

The vertebral implant 110 shown in FIG. 10 is configured to restoremotion between vertebral bodies. In other procedures, such asvertebrectomies or corpectomies, one or more vertebral bodies areremoved and an implant is inserted in the space left by the removedvertebrae. These types of devices include multiple components similar tothe implant 110. For example, FIG. 11 illustrates an exemplarycorpectomy device 210 in which an expandable cage 216 is disposedbetween end plates 212, 214. Other types of devices may include spacers,rods, or other fixed or expandable members spanning a distance betweenfirst and second end plates 212, 214. As illustrated, osteoconductiveinserts 230, 232 may be incorporated onto a non-osteoconductive resinsubstrate 234, 236 to promote bone growth at respective bone-contactsurfaces.

An exemplary process for making the vertebral implants may include stepsof providing an osteoconductive insert comprising a bone contact surfaceand a substrate interface, orienting a matrix of fibers to extendoutward from the interface surface, and forming a body constructed atleast partially from a biocompatible polymer into the substrateinterface and around the matrix of fibers. Forming the body in thismanner may include extending the matrix of fibers into the body betweenabout one and two millimeters. Furthermore, it may be appropriate toorienting the matrix of fibers substantially transverse to the substrateinterface. The osteoconductive insert may be positioned to coversubstantially the entire bone contact surface of the vertebral implant.The matrix of fibers may comprise carbon fibers or metal fibers.

Another exemplary process for making the vertebral implants may includesteps of preforming an osteoconductive insert, inserting theosteoconductive insert into a mold, introducing a biocompatible polymerinto the mold and forcing the biocompatible polymer into contact withthe insert, and causing the polymer to cure within the insert so thatthe insert forms a bone contact surface of the vertebral implant. Theseprocess steps may further include positioning the osteoconductive insertto form substantially all of the bone contact surface of the vertebralimplant. The preforming process may include exemplary processes such asmolding osteoconductive material to form the osteoconductive insert andforming a porous matrix of fibers into the osteoconductive insert.Furthermore, the step of forcing the polymer into contact with theinsert further may cause the polymer to cure around a matrix of fibersthat extend outward from an outer surface of the osteoconductive insert.

The osteoconductive inserts are not limited to vertebral implants. Forexample, osteoconductive inserts may be incorporated into otherorthopedic implants formed from a non-osteoconductive resin such astibial and femoral knee components, hip stems, and acetabular cups 300such as that shown in FIG. 12. The illustrated cup 300 includes asubstrate portion 302 that is sized and shaped to accept a femoral stem310. An osteoconductive insert 304 is formed onto the substrate 302. Theacetabular cup 300 may be molded using the process steps similar to thatdepicted in FIGS. 5A-5D.

Furthermore, embodiments disclosed above have not included anyparticular surface geometry, coating, or porosity as are found inconventionally known vertebral implants. Surface features such as theseare used to promote bone growth and adhesion at the interface between animplant and a vertebral end plate. Examples of features used for thispurpose include, for example, teeth, scales, keels, knurls, androughened surfaces. Some of these features may be applied throughpost-processing techniques such as blasting, chemical etching, andcoating, such as with hydroxyapatite. The bone interface surfaces,including the osteoconductive inserts, may also include growth-promotingadditives such as bone morphogenetic proteins. Alternatively, pores,cavities, or other recesses into which bone may grow may be incorporatedvia a molding process. Other types of coatings or surface preparationmay be used to improve bone growth into or through the bone-contactsurfaces. However, the inserts that include these types of features maystill be formed and characterized by the aspects disclosed herein.

Spatially relative terms such as “under”, “below”, “lower”, “over”,“upper”, and the like, are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the device in additionto different orientations than those depicted in the figures. Further,terms such as “first”, “second”, and the like, are also used to describevarious elements, regions, sections, etc and are also not intended to belimiting. Like terms refer to like elements throughout the description.

As used herein, the terms “having”, “containing”, “including”,“comprising” and the like are open ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

The present invention may be carried out in other specific ways thanthose herein set forth without departing from the scope and essentialcharacteristics of the invention. For instance, the implant 10 depictedin FIGS. 2-9 may be described as an ALIF device, implantable from ananterior approach. However, the osteoconductive inserts may beincorporated in other types of vertebral implants, including but notlimited to TLIF or PLIF devices. The present embodiments are, therefore,to be considered in all respects as illustrative and not restrictive,and all changes coming within the meaning and equivalency range of theappended claims are intended to be embraced therein.

1. A vertebral implant device for insertion between vertebral bodies ina patient, the implant comprising: an insert comprising a first bonecontact surface and an opposing second surface, the insert constructedfrom an osteoconductive material with fibers with some of the fibersincluding a first section positioned in the insert and a second sectionthat extends outward from the second surface, the insert also includingan anchor that extends outward from the second surface a greaterdistance than the second sections of the fibers; and anon-osteoconductive body attached to the second surface of the insertand being formed from a different material than the insert; the secondsections of the fibers and the anchor being positioned in the body; theinsert and the anchor having a unitary construction formed from theosteoconductive material.
 2. The vertebral implant of claim 1, whereinthe fibers include carbon fibers.
 3. The vertebral implant of claim 1,wherein the fibers include metallic filaments.
 4. The vertebral implantdevice of claim 1, wherein the fibers that extend outward from thesecond surface are aligned approximately perpendicular to an interfacebetween the insert and the body.
 5. The vertebral implant device ofclaim 1, wherein the anchor includes a stem that extends outward fromthe second surface of the insert and an enlarged head spaced away fromthe second surface of the insert, the enlarged head including a greaterwidth than the stem.
 6. The vertebral implant device of claim 5, whereinthe head includes a major axis that is approximately perpendicular tothe stem.
 7. The vertebral implant device of claim 1, wherein the insertincludes a smaller thickness than the body.
 8. The vertebral implantdevice of claim 1, wherein an additional number of the fibers arecompletely embedded within the insert.
 9. A vertebral implant device forinsertion between first and second vertebral bodies in a patient, theimplant comprising: a body constructed from a first material and havinga first side and an opposing second side; an insert attached to thefirst side of the body and being constructed from a second materialhaving a plurality of fibers; an anchor that extends outward from theinsert into the body, the anchor including a stem adjacent to the insertand a head spaced away from the insert and positioned at an end of thestem, the stem including a smaller width than the head; and the anchorand a portion of the plurality of fibers extending outward from theinsert and into the body to improve adhesion between the body and theinsert.
 10. The vertebral implant device of claim 9, wherein theplurality of fibers are aligned approximately perpendicular to aninterface between the body and the insert.
 11. The vertebral implant ofclaim 9, wherein the plurality of fibers includes one of carbon fibersand metallic filaments.
 12. The vertebral implant device of claim 9,wherein the insert extends completely across the first side of the bodyand includes a smaller thickness than the body.
 13. The vertebralimplant device of claim 9, wherein a second portion of the plurality offibers are completely embedded within the insert.
 14. A vertebralimplant device for insertion between first and second vertebral bodiesin a patient, the implant comprising: an intermediate portionconstructed of a first material and including a first side and a secondside; a first insert attached to the first side of the intermediateportion and including a first contact surface configured to contactagainst the first vertebral body when the vertebral implant device isinserted in the patient; a second insert attached to the second side ofthe intermediate portion including a second contact surface configuredto contact against the second vertebral body when the vertebral implantdevice is inserted in the patient; each of the inserts being constructedfrom a second material with a plurality of fibers, a portion of theplurality of fibers of each of the first and second inserts extendinginto the intermediate portion; a plurality of anchors that extendoutward from the first and second inserts and into the intermediateportion, each of the plurality of anchors including a stem adjacent tothe insert and a head spaced away from the insert and positioned at anend of the stem.
 15. The vertebral implant device of claim 14, whereinthe first insert and at least one of the plurality of anchors areintegrally formed from the second material and have a one-piececonstruction.
 16. The vertebral implant device of claim 15, wherein thesecond insert and at least another one of the plurality of anchors areintegrally formed from the second material and have a one-piececonstruction.
 17. The vertebral implant device of claim 14, wherein theportion of the plurality of fibers that extend outward from the firstinsert are aligned approximately perpendicular to an interface betweenthe intermediate portion and the first insert.
 18. The vertebral implantdevice of claim 17, wherein the portion of the plurality of fibers thatextend outward from the second insert are aligned approximatelyperpendicular to an interface between the intermediate portion and thesecond insert.
 19. The vertebral implant of claim 16, wherein theplurality of fibers include one of carbon fibers and metallic filaments.20. The vertebral implant device of claim 15, wherein each of the firstand second inserts include a smaller thickness than the intermediateportion.